Has anyone used motionmailapp.com to create a countdown timer for Marketo emails? What has your experience been? Has it impacted your mailing's deliverability or tripped up people's spam filters, or displayed script warnings to users?
You wouldn't have script warnings as it's an animated GIF, not a script (scripts don't work in email under any circumstances).
Depending on how long your offer lasts, the GIF can be very large, and therefore decreases your text-to-image ratio (a standard anti-spam check). It's ingenious technology, though. You could give it a try in an A/B scenario. (We don't sell any stuff that would work in this context, so I haven't tried it.)